1. Field of the Invention
The invention relates to an apparatus for reversibly storing digital data as error protected product codewords on a multitrack record carrier. In particular, the record carrier may be a magnetic cassette tape that has a plurality of parallel recording tracks. Alternatively the "tracks" could be successive revolutions of what is effectively a spiral on a disk, such as an optical recording disk. Such storage of digital data is notoriously sensitive to mutilation, which may result in alteration of any arbitrary bit or of long strings of bits along a particular track, particularly bit strings which have patterns having a high error probability. BCH codes over finite fields have proven to be advantageous for error protection, in particular Reed-Solomon codes defined for multi-symbol words, each symbol being an 8-bit element of a finite Galois field, the codes being cyclic at the symbol level. The ordinary-skilled technician could, however, omit various of these code characteristics without deviating from the basic concept of the invention.
2. Background Art
Background information concerning digital audio tape recording and error protection of the recorded digital data can be found in various publications; for example, "Principles of Digital Audio" by K. C. Pohlmann, 2d ed. 1989, H. Sems & Co., and "Error Control Coding" by S. Lin et al, 1983, Prentice-Hall, Inc.